Opa-Based Optical Scanner System Using Metalens

The present application claims priority to Korean Patent Application No. 10-2024-0086467, filed Jul. 1, 2024, the entire contents of which are incorporated herein for all purposes by this reference.

The present disclosure relates to an OPA-based optical scanner system using a metalens, and more particularly, to an optical scanner system that focuses or diffuses light output from an optical phased array antenna using a metalens.

A LIDAR sensor for autonomous vehicles obtains 3D space information by measuring the time that an incident pulse laser takes to return after reflecting from an object. A LiDAR is, in a broad sense, classified into a “flash type” and a “scanning type” in accordance with the type of laser emission. The flash type is a method of simultaneously emitting laser beams to a wide area, in which a light receiving element is a 2D-array type such that a receiver can also recognize an image returning after reflecting. On the other hand, a scanning LiDAR performs point mapping if a 3D space by vertically and horizontally rotating a laser beam. Accordingly, it has a lower laser light source output and a simple light reception structure of the receiver in comparison to the flash type. An existing scanning LiDAR has a field of view of 360° by mechanical motor rotation.

However, in a basic mechanical LiDAR, the motor for rotation is heavy and a significant amount of power is consumed, so the mechanical LiDAR cannot be applied to unmanned aerial vehicles with limited power and weight requirements and the mechanical rotation speed does not meet the rotation speed required for autonomous vehicles to operate on highways.

An optical phased array antenna can distribute an incident laser to each antenna element through multiple directional couplers and can achieve desired propagation directions of output lasers by modulating the phase of the distributed lasers. In the case of a LiDAR with an optical phased array antenna in the related art, collimating lenses and expanding lenses are used to focus and diffuse the light emitted from the optical phased array antenna. However, such collimating lenses and expanding lenses have a relatively large volume, which makes it difficult to miniaturize a scanning system.

(Patent Document 1) Registration No. 10-1924890: Optical Phased Array Antenna and LiDAR Having The Same

The present disclosure has been made in an effort to solve the problems described above and an objective of the present disclosure is to provide an OPA-based optical scanner system using a metalens that can focus or diffuse the light emitted from an optical phased array antenna using a metalens, instead of collimating lenses and expanding lenses that are widely used.

In order to achieve the objectives of the present disclosure, an OPA-based optical scanner system using a metalens according to the present disclosure includes: an optical phased array antenna configured to modulate a phase of light input from a light source unit and output the light, and an optical unit installed on a path of light output from the optical phased array antenna and configured to focus or diffuse light output from the optical phased array antenna using a metalens.

The optical unit may include: a first metalens installed on a path of light output from the optical phased array antenna and configured to focus the light; and a second metalens installed on a path of light emitted from the first metalens and configured to diffuse the light.

The first metalens may include: a first main substrate installed on a path of light output from the optical phased array antenna and transmitting the light; and multiple first meta-atoms formed on an exit surface of the first main substrate, through which light incident from the optical phased array antenna is emitted, to focus light passing through the first main substrate.

The first meta-atoms may protrude from a surface of the first main substrate and may be spaced apart from each other.

The first meta-atoms may be formed to have a circular cross-section with a predetermined radius.

The second metalens may include: a second main substrate disposed on a path of light emitted from the first metalens, through which the light passes; and multiple second and third meta-atoms respectively formed on an incident surface of the second main substrate to which light emitted from the first metalens is incident, and an exit surface of the second main substrate from which the light is emitted, in order to diffuse light passing through the second main substrate.

The second meta-atoms may protrude with respect to the incident surface of the second main substrate and may be spaced apart from each other.

The second meta-atoms may be formed to have a circular cross-section with a predetermined radius.

The third meta-atoms may protrude with respect to the exit surface of the second main substrate and may be spaced apart from each other.

The third meta-atoms may be formed to have a circular cross-section with a predetermined radius.

The OPA-based optical scanner system using the metalens according to the present disclosure has the advantages that it can achieve miniaturization by reducing the size of the system because the light emitted from the optical phased array antenna is focused and diffused by metalens, it is easy to manufacture through semiconductor processes, allows for mass production for commercialization, and improve system efficiency by enabling precise control of light focusing and diffusion.

Hereafter, an OPA-based optical scanner system using a metalens according to an embodiment of the present disclosure is described in detail with reference to the accompanying drawings. The present disclosure may be modified in various ways and implemented by various exemplary embodiments, so specific exemplary embodiments are shown in the drawings and will be described in detail herein. However, it is to be understood that the present disclosure is not limited to the specific exemplary embodiments, but includes all modifications, equivalents, and substitutions included in the spirit and the scope of the present disclosure. Similar reference numerals are assigned to similar components in the following description of drawings. In the accompanying drawings, the dimensions of structures were exaggerated larger than the actual dimensions to make the present disclosure clear.

Terms used in the specification, “first”, “second”, etc., may be used to describe various components, but the components are not to be construed as being limited to the terms. The terms are used only to distinguish one component from another component. For example, the “first” component may be named the “second” component, and vice versa, without departing from the scope of the present disclosure.

The terms used herein are used only for the purpose of describing particular embodiments and are not intended to limit the present disclosure. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” or “have” used in this specification specify the presence of stated features, steps, operations, components, parts, or a combination thereof, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or a combination thereof.

Unless defined otherwise, it is to be understood that all the terms used in the specification including technical and scientific terms have the same meanings as those that are generally understood by those who skilled in the art. It will be further understood that terms such as terms defined in common dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

1 FIG. 2 FIG. 100 andshow an OPA-based optical scanner systemusing a metalens according to the present disclosure.

100 300 200 400 300 300 Referring to the drawings, the OPA-based optical scanner systemusing a metalens includes an optical phased array antennathat modulates the phase of light input from a light source unitand outputs it, and an optical unitthat is installed on a path of the light output from the optical phased array antennaand focuses or diffuses the light output from the optical phased array antennausing a metalens.

200 210 220 210 300 The light source unitincludes a laser light sourcethat generates light, and an optical amplifierthat amplifies the light output from the laser light sourceand outputs it to the optical phased array antenna.

210 220 220 210 210 220 210 220 220 300 300 300 220 221 As the laser light source, a laser generator (Tunable Laser Source (TLS)) that supplies a laser beam to the optical amplifieris applied. As the optical amplifier, an amplification device (Erbium-Doped Fiber Amplifier (EDFA) for amplifying the laser beam input from the laser light sourceis applied. Since a laser light sourceand an optical amplifierthat are commonly used in LiDAR systems of the related art are applied as the laser light sourceand the optical amplifier, and a detailed description is omitted. The optical amplifieris connected to the optical phased array antennathrough an optical fiber and outputs amplified light to the optical phased array antenna. The optical phased array antennais connected to the optical fiber connected to the optical amplifierthrough an optical fiber connector.

300 221 200 300 300 The optical phased array antenna, though not shown in the figures, includes a coupling part connected to the optical fiber connectorand receives the light output from the light source unit, a phase modulation module that modulates the phase of the light input from the coupling part, and an optical output part that outputs the modulated light from the phase modulation module and has an antenna element waveguide extended to a predetermined length to propagate the light. Meanwhile, an optical phased array antennacommonly used in LiDAR systems of the related art is applied as the optical phased array antennadescribed, and thus a detailed description is omitted.

400 410 300 420 410 The optical unitincludes a first metalensthat is installed on the path of the light output from the optical phased array antennaand focuses the light, and a second metalensthat is installed on the path of the light emitted from the first metalensand diffuses the light.

410 411 300 412 300 411 The first metalensincludes a first main substratethat is installed on the path of the light output from the optical phased array antennaand transmits the light, and multiple first meta-atomsthat is formed on the exit surface of the first main substrate, through which the light incident from the optical phased array antennais emitted, to focus the light passing through the first main substrate.

411 411 300 2 FIG. 2 The first main substrateis formed in a disc shape with a predetermined thickness. In this configuration, referring to, the first main substrateis made of silicon dioxide (SiO) so that the light output from the optical phased array antennacan pass through.

412 411 411 412 411 411 412 412 The first meta-atomsare formed to protrude on the surface of the first main substrate, and are formed on the exit surface of the first main substratethat is the opposite side of the incident surface where light is incident. The first meta-atomsprotrude to a predetermined height with respect to the exit surface of the first main substrate. In this configuration, the propagation direction of light refers to the propagation direction of light passing through the first main substrate. The first meta-atomsare spaced apart from each other, and it is preferable that they are formed in the shape of a circular disc having a predetermined radius. The first meta-atomsare made of silicon (Si).

3 FIG. 4 FIG. 3 FIG. 4 FIG. 5 FIG. 411 412 Meanwhile, inand, simulation results for the metalens configured with the first main substrateand first meta-atomdescribed above are shown.shows the phase change of light passing through the metalens according to the protrusion height H of the meta-atoms and the radius R of the meta-atoms relative to the main substrate, whileshows the transmission change of light passing through the metalens according to the protrusion height H of the meta-atoms and the radius R of the meta-atoms relative to the main substrate. Further, a graph of FDTD (Finite Difference Time Domain) simulation results for the structure of the metalens is shown in. In this configuration, the protrusion height H of the meta-atoms relative to the main substrate is 880 nm, the period P of the meta-atoms is 860 nm, and the wavelength λ of light is 1550 nm. Meanwhile, the following Table 1 shows the result values of the phase change of light according to the change in the diameter of the meta-atoms.

TABLE 1 Diameter of meta-atom, 2R Phase (nm) (degree) 200 0 267 22 296 45 310 67 318 90 326 112 334 135 339 157 343 180 350 202 357 225 362 247 372 270 384 292 399 315 423 337

6 FIG. 410 411 411 412 411 411 0 1 1 2 3 0 1 ϕ o Referring to the figures and Table 1, it can be seen that the light phase and light transmission of the metalens change as a function of the radius and protrusion height of the meta-atoms. In particular, meta-atoms with a diameter ranging from 200 to 423 nm can provide relatively complete phase control. Therefore, by changing the shape and arrangement of the meta-atoms, it is possible to manufacture metalenses that provide functions similar to various types of lenses (such as convex lenses, concave lenses, and axicon lenses). Meanwhile,is a conceptual diagram of the first metalens. In this case, the left surface rof the first main substrateis the incident surface to which light is incident, and the right surface rof the first main substrateis the exit surface from which light is emitted. Multiple meta-atomsare formed on the exit surface of the first main substrate. Further, k, k, and krepresent the incident, transmitted, and refracted vectors of light, respectively.ϕand ϕrepresent the phase distribution at the incident surface and the exit surface of the first main substrate.

300 410 411 412 410 300 1 2 3 As shown in the figures, the light emitted from the optical phased array antennaenters the first metalensalong the path of k, is transmitted along the path of k, and is refracted along the path of kat the exit surface of the first main substrateon which the first meta-atomsare provided. As described above, the first metalensfocuses light output from the optical phased array antenna.

7 FIG. 9 FIG. 7 FIG. 8 FIG. 9 FIG. 300 410 410 300 410 410 410 300 410 Meanwhile,toshow the experimental results of the beam collimation characteristics of the optical phased array antennaimplemented with the first metalens.andshow phase masks for the x-axis and y-axis of the first metalens, and light paths, andis a graph comparing the spot size of light output from the optical phased array antennadepending on the presence or absence of the first metalens. In these figures, the cyan region is the spot of light that has passed through the first metalens, and the blue region is the spot of light that has not passed through the first metalens. Referring to the figures, it can be seen that the light that has passed through the optical phased array antennais focused by the first metalens.

420 421 410 422 423 421 410 Meanwhile, the second metalensincludes a second main substratethat is disposed on the path of the light emitted from the first metalensand through which the light passes, and multiple second and third meta-atomsandrespectively formed on the incident surface of the second main substrateto which the light emitted from the first metalensis incident, and the exit surface of the second main substrate from which the light is emitted, in order to diffuse the light passing through the second main substrate.

421 421 411 410 2 The second main substrateis formed in a disc shape with a predetermined thickness. In this configuration, the second main substrateis made of silicon dioxide (SiO), in the same manner as the first main substrate, so that the light that has passed through the first metalenscan pass through it.

422 421 421 422 421 422 422 The second meta-atomsare formed to protrude on the surface of the second main substrate, and are formed on the incident surface of the second main substrateto which light is incident. In this configuration, the second meta-atomsprotrude in the opposite direction to the propagation direction of light with respect to the incident surface of the second main substrate. The second meta-atomsare spaced apart from each other, and it is preferable that they are formed in the shape of a circular disc having a predetermined radius. The second meta-atomsare made of silicon (Si).

423 421 421 423 421 423 423 422 The third meta-atomsare formed to protrude on the surface of the second main substrate, and are formed on the exit surface of the second main substratefrom which light is incident. In this configuration, the third meta-atomsprotrude in the propagation direction of light with respect to the exit surface of the second main substrate. The third meta-atomsare spaced apart from each other, and it is preferable that they are formed in the shape of a circular disc having a predetermined radius. The third meta-atomsare made of silicon (Si) to correspond to the second meta-atoms.

10 FIG. 11 FIG. 12 FIG. 420 421 421 422 423 421 300 420 420 1 2 1 2 300 420 0 1 1 2 3 1 2 3 Meanwhile,is a conceptual diagram of the second metalens. In this case, the left surface rof the second main substrateis the incident surface to which light is incident, and the right surface rof the second main substrateis the emission surface from which light is emitted. Multiple meta-atomsandare formed on the left surface and the right surface of the second main substrate, respectively. Further, k, k, and krepresent the incident, transmitted, and refracted vectors of light, respectively. In this state, an experiment was conducted on the expansion of the field of view of light output from the optical phased array antennausing the second metalens.andshow phase masks of the incident surface and exit surface of the second metalens, that is, the metasurfacesand, in which the phase masks of the metasurfacesandhave focal lengths of 900 μm and 300 μm, respectively, and a radius of 200 μm. The 64-channel optical phased array antennaprovides a field of view (FoV) of approximately 15 degrees, and the inclination of the light incident vector with respect to the second metalensis given as 7.5 degrees. The optical path coordinates for the vectors k, k, and kare as shown in the following Equation 1.

420 420 420 According to the experimental results, as shown in the figures, it can be seen that the light incident on the second metalensat an angle of 7.5 degrees is emitted and output at approximately 20.98 degrees. That is, the field of view of light is amplified by approximately three times by the second metalens. Accordingly, the second metalenscan be effectively used to expand the field of view of incident light.

100 300 The OPA-based optical scanner systemusing the metalens configured as described above in accordance with the present disclosure has advantages it the that can achieve miniaturization by reducing the size of the system because the light emitted from the optical phased array antennais focused and diffused by metalens, it is easy to manufacture through semiconductor processes, allows for mass production for commercialization, and improve system efficiency by enabling precise control of light focusing and diffusion.

The description of the proposed embodiments is provided to enable those skilled in the art to use or achieve the present disclosure. Various modifications of the embodiments would be apparent to those skilled in the art, and general principles defined herein may be applied to other embodiments without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments proposed herein and should be construed in the widest range that is consistent with the principles proposed herein and new characteristics.